1. Field of the Invention
The present invention relates to surge protection devices and, in particular, relates to a miniature solid state surge protection device for use on telephone central office communication line terminal blocks, or the like, to provide a overvoltage and overcurrent or fail short protection.
2. Discussion of the Relevant Art
Overvoltage and overcurrent (fail short) surge protectors for communication lines are abundant in the art and they are generally directed to protect the instruments at the point of installation, e.g. home or business. Typical of these devices are U.S. Pat. No. 4,701,825 issued to E. J. Pagliuca on Oct. 20, 1987; U.S. Pat. No. 4,603,368 issued to E. J. Pagliuca on Jul. 29, 1986; and U.S. Pat. No. 4,351,015 issued to T. J. Smith on Sep. 21, 1982. All of these devices are installed at the terminals of the equipment to be protected and are generally unsuitable for use at a telephone central office. U.S. Pat. No. 4,424,546 issued to T. J. Smith on Jan. 3, 1984 is the only one of the above noted patents that is suitable for use at a telephone central office.
Typical of the terminal blocks used for connecting the telephone communication lines are those manufactured by Reliable Electric Company, Franklin Park, Ill., Model Number R713-1,2,3 or 4 or terminal blocks manufactured by TII Industries, Inc., Model Number TII 561/571 Series Building-Entry Protector Assemblies. These terminal blocks are utilized by telephone central office installations or at the entrance to buildings where a large number of telephone communication lines are provided. The terminal boards are adapted to receive protective modules such as Model Number 4AB, manufactured by Reliable Electric Company of Franklin Park, Ill., and are suitable for receiving the protector modules of the instant invention.
Earlier devices which were used at telephone central office installations either in connection with or proximate to central office terminal blocks that were utilized in the central office termination of communication lines require installation separate and apart from central office communication line terminal blocks and are large in size and, since they were not directly mounted on the terminal blocks but remote therefrom, do not always provide adequate protection to the lines. The solid state miniaturized devices as disclosed herein mount directly to the terminal blocks and afford a higher degree of protection. However, in order to improve reliability, insure protection and utilize the module cover as a dust cover, in addition to having access to the line terminals, a different assembly technique is required.
The present apparatus is small in size, may be mounted upon the central office communication line terminal block, is readily removable therefrom should it be necessary to replace a defective unit, provides for the replacement of the miniature solid state surge protector device and additionally includes overcurrent or fail short protection for the communication lines. When an overcurrent occurs on the communication line or if an overvoltage transient damages the overvoltage surge protector, the present surge protector provides a positive shorting connection between the communication line and ground.
Therefore, it is an object of the present invention to provide an economical, miniature central office surge protector apparatus capable of being used with central office communication line terminal blocks.
It is another object of the present invention to provide a miniature central office surge protector apparatus that protects for excessive line currents as well as overvoltage surges.
It is yet a further object of the present invention to provide a miniature surge protector apparatus that utilizes a solid state overvoltage protection device.
It is yet another object of the present invention to provide a miniature surge protector apparatus suitable for use on central office terminal blocks wherein the overvoltage solid state protection device may be readily removed and replaced.
It is still yet another object of the present invention to provide a miniature surge protector apparatus suitable for central office terminal blocks that is capable of providing fail short protection with a line current overload.